Expanded – threaded – driven – headed – tool-deformed – or locked-thr – With means to indicate application of predetermined... – Axially deformable member or portion
Reexamination Certificate
2000-04-17
2001-06-26
Wilson, Neill (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
With means to indicate application of predetermined...
Axially deformable member or portion
C411S014000, C073S761000, C116S212000
Reexamination Certificate
active
06250863
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of load sensors and more particularly to a washer having strain gauges for measuring axial forces applied to the washer.
2. Background Art
There are numerous applications where it would be highly advantageous to be able to measure axial load in a washer. For example, such a capability would permit extremely accurate application of clamping forces produced by a nut and bolt assembly of which the washer were a component. Another example is for measurement of the load on a hook supported by the washer in combination with a nut or other fastener. The use of strain gauges to measure force applied to a structure is a well-known application. By way of example, U.S. Pat. No. 5,872,320 discloses a force transducer which may be used in a computer keyboard to control the position of the cursor on a display screen. As shown in that patent, the strain gauges are typically configured in a bridge arrangement. Connecting the strain gauges in a bridge circuit provides a larger signal swing which results in greater resolution and also renders the output signal relatively insensitive to temperature variation which could otherwise alter the characteristics of the transducer with changes in ambient temperature.
Use of strain gauges in a small mechanical device like a washer, the entire structure of which is subjected to substantially the same axial forces, makes it difficult to connect strain gauges in a bridge configuration and thereby achieve the advantages of greater output signal amplitude swing and temperature insensitivity.
It would be highly advantageous if it were possible to provide a washer with strain gauges configured in a bridge arrangement where the performance improvements of true bridge operation could be realized.
SUMMARY OF THE INVENTION
The present invention comprises a washer having a plurality of strain gauges, at least one of which is positioned on a portion of the washer subjected to axial force and at least one of which is positioned on a portion of the washer not subjected to axial force. In a preferred embodiment, each such washer portion has two strain gauges and the total of four strain gauges are connected into a common bridge circuit. In the preferred embodiment the portion of the washer not subjected to axial force is a wedge partially cut into the washer structure and shortened axially to form a gap between the wedge and a surface abutting the washer. In this manner, axial force applied to the washer is not applied to the wedge. The resulting strain gauge configuration provides an electrical signal indication of axial stress that is high resolution and temperature insensitive.
OBJECTS OF THE INVENTION
It is therefore a principal object of the present invention to provide a washer having a plurality of strain gauges affixed to the washer for measuring axial load.
It is another object of the invention to provide a washer having a plurality of strain gauges connected in a bridge circuit for generating an output indicative of axial forces on the washer.
It is still another object of the invention to provide a washer for use with a plurality of strain gauges, at least one of the strain gauges being affixed to a portion of the washer subjected to axial forces and at least another of the strain gauges being affixed to a portion of the washer not subjected to axial forces.
It is another object of the invention to provide a washer having an axial surface and a radial surface, the radial surface providing a plurality of locations for affixed strain gauges for indicating axial forces directed at the axial surface, a portion of the axial surface being isolated from the remaining axial surface to provide a substantially zero axial force region of the washer.
REFERENCES:
patent: 4106370 (1978-08-01), Kraus et al.
patent: 4553124 (1985-11-01), Malicki
patent: 2212284 (1989-07-01), None
Kamentser Boris
Kamentser Eugenia
Tachner Leonard
Wilson Neill
LandOfFree
Washer having stressed and unstressed strain gauges does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Washer having stressed and unstressed strain gauges, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Washer having stressed and unstressed strain gauges will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2454854